Multi-function hydraulically operated devices which operate at a location which may be movable in one or more directions in relation to the connected hydraulic system requires connecting hydraulic conduits to be movably mounted so that the terminus of hydraulic conduits are continuously connected to the moving device. Examples of such remote devices include multi-function attachments mounted for elevation on telescopic lift truck uprights, devices mounted for operation from the end of telescopic crane or boom mechanisms, and others.
This background and our invention will be described with particular reference to hydraulic control systems for lift truck attachments, but it will be understood that our invention has much wider application as indicated by the title hereof.
As is well-known in the exemplary field of lift trucks, a large variety of attachments have been designed for support by a carriage, conventionally known as a fork carriage, which is elevatable in a telescopic upright for performing various functions for which the attachment may be designed at any selected elevation of the carriage and upright. Such attachments may, for example, be of types known as side shifting clamps, rotating roll clamps, side loaders, and others. Thus, it is required, depending upon the number of functions or operations which the attachment is designed to perform, that a plurality of flexible hydraulic conduits plus, in some instances, electric lines which connect with switching solenoid valves on the lift carriage, for example, be connected from the truck hydraulic system to the attachment by reeving the conduits and lines in the upright, or adjacent to it, for vertical movement with the carriage.
Various means have been devised heretofore for improving the handling and routing of hoses and electric lines in such applications, examples of which are described and claimed in the dual hose reel U.S. Pat. No. 3,709,252, and the internal upright reeving of hydraulic conduits and electric lines as disclosed in U.S. Pat. Nos. 3,462,028 and 3,491,905, all of common assignee. As is well known to persons skilled in the art, disadvantages multiply with the addition of attachment fucntions which necessitate the addition of more hydraulic conduits and/or electric lines reeved on the upright to travel with the lift carriage. Such disadvantages include interference with operator visibility through the upright, greater probability of rupture or breakage of multiple hydraulic and electric lines, relatively high cost, both initial and in maintenance, and others. One design to minimize the number of such conduits, which in operating some lift truck attachments have heretofore required as many as eight upright reeved hoses, is exemplified by U.S. Pat. No. 3,692,198, also of common assignee. It dislcoses a structure for reducing the required number of upright reeved conduits to as few as three in relation to a side shifting clamp attachment.
We have devised a hydraulic system for use in such lift truck applications, for example, which is capable of operating an attachment having a plurality of operating functions with as few as two hydraulic conduits reeved in the upright, and with no electric lines reeved therein for connection to carriage mounted solenoid valves as previously used in certain attachment applications.